Hey guys I recently put in a new reman moter from Titan Engines and with in 3k miles theres now a hole in cylinder 6. I heard the infamous detonation nosie only accelerating but thought it was something else besides the motor. I unfortunately threw parts at the jeep to try and fix it but eventually learned it was detonation. Titan said that the warranty was voided but it was repairable however the issue needs to be located. Here a pic of the cylinder

 

What spark plugs do (did) you have in it? What gas octane did you use?

What is the liquid all over the piston and rod? I can see coolant up near the top of the cylinder.

Is the cylinder badly scored? Hard to tell from your picture.

At the 4 o'clock position, is that signs of the piston melting?

What do the other pistons look like?

 

When I installed the motor I got some ngk spark plugs and have been running regular but recently put mid grade in it. The liquid is coolant from removing the head, I forgot to drain the block. The cylinder is slightly scored but I think it might be fine be if it got honed. Yeah I think the piston is melted in the 4 o'clock area. Would that causes the detonation issue? Here's the pictures of the other cylinders.

 

So I mean to start a long thread about pre-ignition/pinging/detonation

That is because I detected it in my 250k motor, and it is pretty well known that piston melting is one of the few weakness of the 4.0

The first thing I am going to say in your case, with a "reman" engine is wonder whether they have shaved the head, making the compression ratio higher ??

In my case, the head is unknown, as it had near 200k when I got it, but I am going to assume its original and stock

I noticed the distinct sound of rivets being shaken in a biscuit tin, my (correct) spark plugs 3.5yrs, but only 25k miles, change them out for same, problem reduced

Still present under hard throttle uphill

Did a couple of Italian tuneups (drive as hard as possible for + 1 hour) ...burns excess carbon in combustion chamber

problem reduced but still present

Consult local XJ owners

they tell me this (first I have to explain US and Oz Octane ratings are different)

So... Oz 91= US 87

OZ E10 unleaded 94 = US 91

We also have 95 and 98 for high compression vehicles

My user manual states the XJ is fine for OZ 91 or E10 94

The tip I got was 91 is not enough, especially when warm, use 94..so I did, and its almost fixed, but not 100%

So I view live data via OBD2. The Short term fuel trim is not perfect and has a few red highlights, which I believe means its out of spec

next front O2..same thing

I am now thinking my front O sensor, of which I have no idea how old may be a possible culprit

Trouble is, non-OEM replacements are not very reliable

Anyway, there is some info for youse

for the OP, I believe its critical to establish head thickness. There should be a spec somewhere

If you take close look and pics at underside of head, many heads have stamped tabs, and you can tell if they have been machined cause the stampings are machine away

post some pics of that, and the experienced XJ head guys round here may be able to say

95 and especially 98 are much more expensive and there should be no need to run them in an XJ. I do have to run 98 in my 9.5:1 Jaguar 4.2 I6

My mate who was a mechanic over 60 yrs would just pull that piston, hone the bore, and put another one in (saw him do that on an XJ)

 

What's the number(s) on the spark plugs? Trying to identify the heat range.

What does the combustion chamber look like?